Typical methods for producing electronic assemblies may use various thermal processes for producing the contacts between the circuit carrier and the components, in particular soldering processes. The thermal processes also cause thermal loading during production. To protect components that are particularly thermally sensitive, modified soldering processes, which for example proceed in a number of stages, therefore may be used. This causes additional production and assembly costs. A further problem arises if the electronic assembly to be produced is heterogeneous in its heat conducting properties and thermal capacity. If a thermal joining process is used for the contacts, varying degrees of heating within the electronic assembly then occur in the production device, such as for example the soldering furnace. This can lead to the formation of additional stresses, and consequently reduce the reliability of the electronic assembly produced. Although this effect can be counteracted by extending the heating times for the electronic assemblies to be produced, so the heat is distributed better across the assembly, this also results in longer throughput times in the production plant, whereby the cost-effectiveness of the process is reduced.
One way of improving the thermal characteristics, in addition to the heat applied by the production plant and introduced from outside into the electronic assembly to be produced, is to include a heat source that generates heat in the electrical assembly itself. For example, some include sheet-like components, such as printed circuit boards, with reactive foils which under certain conditions generate heat in the sheet-like component. An electronic assembly to be produced could in this way be heated up as it were from the inside out, while this heat could supplement the heat of the production device that is introduced from outside.
In some examples, a reactive soldering material is used as the material for the electrical contacts. Added to this material is a reactive component, which reacts exothermically at a reaction temperature, and thereby provides heat. This heat is directly available in the soldered connections to be formed, for which reason they are heated up more than the rest of the electronic assembly. The production device can therefore be operated at a lower temperature, the amount of heat that is present in the solder material being sufficient altogether to contribute to a melting of the solder. The reactive materials may transformed in the course of the exothermic reactions into a reaction product. This remains, at least in residues, on the circuit carrier or in the contact formed (e.g. the soldered connection). The quality of the result of production may be impaired.